What does it mean to be alive?

ATP is not merely a crafting resource. It is the mechanism that converts biological discoveries into player capability. Every major system in the game ultimately either produces ATP, consumes ATP, or exists to increase ATP production. This game mechanic drives exploration and progress through the tech tree, and through player upgrades (see Player Size). The game has a few components in the service of exploration, and energy generation and use.

As the player accumulates more ATP, they can collect it from their structures. When they have enough to meet a certain threshold, player upgrades are unlocked. In addition, two harvesting upgrades are also available: knife (once zinc is discovered) and drill (once iron is discovered). Knife enables the player to kill and harvest soft tissue, and drill enables the player to break through cell walls. Both can also be used in combat with local fauna.

The basic raw materials for building in the game are water, oxygen, phosphorus, fatty acids, ribose, glucose, and glucosamine, though extracellular components can be harvested from other products (muramic acid, glucosamine, and polysaccharides). As with other open world crafting games, the player is tasked with exploring to find new resources, then using those resources to build structures and craftable items. Part of the flow of the game is controlled by discovering specialized biological resources—including trace metals and organism-specific molecules—which are found in different biomes. For example, combining phosphates and fatty acids to build lipids. As you progress, you will need to adaptat in order to build anything in other zones, which can be found in the tech tree.

The cellular structures that you build can help you navigate the environment. One of the earliest structures is the vesicle, which is used for storage. To build this, you learn to create phosphates from phosphorous and oxygen, and to combine those with fatty acids to make lipids. Several lipids can be combined into a sheet of lipids called a membrane, which can be combined to make a multipurpose protocell, a vesicle, and ultimately a cell membrane.

Water

The visor shows the world in terms of its hydrophobic properties (a gradient from water-interacting, blue, to water-repelling, yellow). Managing water interactions and osmotic pressures is a core part of the game, in which the player learns to build membrane-bound structures. Early in the game, the player builds cell walls to counteract osmotic pressure. Later, the player can build cytoskeletons to help maintain their shape, as well as channels and transporters to move water in and out of their structures to maintain osmotic balance.

Turning on the hydrophobicity visor also makes the objects in the world slightly transparent. This lets you see inside of your structures, exposing differences in the cell membrane (bright yellow), and revealing things like vesicle endocytosis.

Progress in Endonaut occurs along three interconnected axes. Exploration unlocks new biomes. Each biome introduces new biological principles that expand the technology tree. As ATP production scales through those technologies (from individual molecules to billions), the Endonaut itself and its equipment can be upgraded, allowing the player to explore increasingly larger and more dangerous environments. Understanding biology unlocks new designs, but only sufficient ATP production and manufacturing capacity allow those designs to be constructed at meaningful scale. You start out the same size as the bacterial cells around you, and you can craft individual ATP molecules. ATP is both the game's energy currency and the primary driver of player progression. When you have enough of it to meet a certain threshold, you can connect to your robot dashboard to physically scale up the Endonaut, increasing its movement speed, hit points, and carrying capacity. As ATP production reaches defined thresholds, the Endonaut chassis can also be upgraded with sci fi systems, listed in the table below. These components influence the way that you can interact with the environment. You can freely scale up or down, up to a maximum of the ATP threshold that you've achieved. If you run out of ATP, your bot will completely power down. You can drop a new bot at a landing zone (respawn), and scrap your previous bot for materials, if you can reach it.

In addition to player upgrades, equpiment upgrades are also available as part of player progression. These are primarily used for finding and harvesting resources, but can also be used in combat with local fauna, if needed.

Exploration and resource extraction from different biomes plays a central role in the game. Exploration and progress through the tech tree are tightly linked, and both in the service of conveying fundamental concepts in life sciences.

Tech Tree

The technology tree maps out player progression through the game. Progress through the tree opens up new capabilities and upgrades. The tree is organized into sugar, protein, and fat branches, which ultimately converge into the process/organelle pathway. Progress through the pathway does not follow a typical linear textbook format, but instead is designed to introduce concepts just as they're needed for survival and progression. Use of a novel technology outside the context of a typical cell helps isolate it to more deeply understand its functionality.

Click to zoom.

Biomes

The game features several biomes, each with unique resources and challenges. Progress through the game requires exploration of these biomes to gather resources and advance through the tech tree, but to be able to fully explore and extract resources, you must progress through the tree. The critical choke points in the game, each of which align with a biological concept, are presented in this figure. At the end of the primordial zone, you're building simple protocells with membranes. These counteract osmotic pressure through the use of a cell wall. When you enter the Fungal Zone, naturally occuring antibiotics will dissolve the cell wall, making it impossible to build structures in this zone until more complex cellular structures can be built. This starts a quest to build eukaryotic cells. At the end of the fungal zone, you have advanced eukarotic structures that are more dynamic, robust, and complex. However, the next zone, the High Oxygen Zone, challenges you to build multicellular structures. For this, you will need a rich source of oxygen, which comes with high levels of oxidation. To overcome this, the player must develop antioxidants. At the end of the High Oxygen Zone, you can connect multiple eukaryotic cells through a shared extracellular matrix and cytoskeletal connections, but to reach the final goal, the occulus in the dome, you must be able to differentiate your cells so that some are harvesting water for your epic megastructure, and some are harvesting light. This is the final challenge of the game, and success puts the player in the sandbox zone with ample resources, where they can build anything.

Click to zoom.

At a high level, the game design philosophy is built around a loop: explore the environment, discover some biological element, use the element to engineer your own systems and tools, use your systems and tools to scale up your energy production, use all of these assets to explore further. Adapting biological systems that we discover is a major characteristic of modern life science along the way towards understanding what life is. Notable examples include polymerase chain reaction and "CRISPR," but of which earned Nobel prizes.

At an implementation level, this loop is manifested in the biomes for exploration, the technology tree that enables buildable structures and craftable elements, and player progression, resulting in expanded capacity for exploration.

The Arid Zone serves as a natural boundary. There are no resources or goals here, just angry, relentless ants that will attack any player on sight.

As you progress, certain construction abilities are unlocked in the game. These menus are ways of designing your builds.

Field Guide

One of the resource categories that you collect is amino acids, and each one must be discovered, except for the one that you start with (glycine). This is the in game screen to track your progress in finding them all.

mRNAs

The mRNA screen is where you construct mRNAs, from which multiple biotools can be built (if you have the resources). Picking the first letter restricts the row, picking the second letter picks the column, and picking the third letter selects the specific amino acid.

mRNA screen. the user interface allows you to pick one of four letters from the first position (which restricts the row), then one of four letters for the second position (which restricts the column), then one of four letters to pick the specific codon.

tRNAs

The tRNA screen is where you construct tRNAs, the interface between mRNAs and proteins.

Endonaut has a few unique settings, including Visual Settings and Engagement Controls.

Visual Settings

Artistic liberties are taken with the visuals at microscopic scale. This is made explicitly clear to players by enabling them to pick the false coloring scheme they prefer, and includes various presets that are aesthetically pleasing, high contrast, or compatible with different forms of color blindness.

Engagement Controls

One of the key features in the game is the ability to directly control the engagement techniques that are used, instead of always maximizing them. For example, the game makes heavy use of Reward Prediction Error (RPE) encoding, as most modern tech does. As long as the cost is low (e.g. checking your phone for a notification) and the reward is unpredictable (e.g. whether or not there's a notification), engagement is strongly encouraged. In the Endonaut (as with other open world crafting games), the cost in terms of time for searching for resources or other rewards is typically fairly low for most resources, and their appearance random, driving engagement.

Because these can be difficult to disengage from, the reward predction schedules can be set to dial back at a certain point (e.g. time-based, milestone based, etc.). After the trigger, the random appearance of rewards gradually (set in the "Timing" box) becomes less over time, until disappearing completely. With the reward schedules no longer driving engagement, disengagement becomes favored. This lets the user take advantage of a highly engaging medium but still have control over healthy play patterns in ways more effective than hard stops.

In game settings screen allowing a player to control how long the highly engaging features of the game are effective. Disengagement can be turned off automatically after a certain amount of time or if some other criteria is met.